1. Field of the Invention
This invention relates to sulfited fats prepared from difficultly sulfitable fats having iodine numbers below 100, to their use as oiling agents for leather and skins and to a process for sulfiting fats having iodine numbers below 100.
2. Statement of Related Art
Sulfited fats used as oiling agents for leather and skins are produced by oxidation of fats with oxygen-containing gas mixtures, for example air, and simultaneous or subsequent sulfitation with alkali and/or ammonium hydrogen sulfite. For fats to be sulfited at all, it is absolutely essential to oxidize them before or during sulfitation by introduction of oxygen-containing gas mixtures. However, since the oxidizability of fats decreases with decreasing iodine number, relatively highly unsaturated fats and oils, i.e. those having iodine numbers above about 100 and preferably above about 130, are normally used (cf. for example "Rauchwarenherstellung und Pelzkonfektion", VEB Fachbuchverlag Leipzig 1970, page 116).
Sulfited fats prepared from sea-animal oils having high iodine numbers, for example whale oil or fish oil, or from vegetable oils having high iodine numbers, for example soya oil, form readily water-emulsifiable substances of high emulsion stability which are particularly suitable for oiling leather and skins. If, by contrast, difficultly sulfitable fats having an iodine number below 100, for example sperm oil, are subjected to oxidizing sulfitation, the oxidation velocity of the fats decreases drastically and products difficult to emulsify in water and having poor emulsion stability are obtained. In order nevertheless to be able to use these sulfitation products for oiling leather and skins, they have to be mixed with emulsifiers or with water-emulsifiable fats which are capable of co-emulsifying the difficulty emulsifiable sulfitation products.